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stack commented on HBASE-8755:
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[~jmspaggi] Thanks boss. What test is this? YCSB w/ how many clients? Thank you sir.
> A new write thread model for HLog to improve the overall HBase write throughput
> -------------------------------------------------------------------------------
>
> Key: HBASE-8755
> URL: https://issues.apache.org/jira/browse/HBASE-8755
> Project: HBase
> Issue Type: Improvement
> Components: wal
> Reporter: Feng Honghua
> Attachments: HBASE-8755-0.94-V0.patch, HBASE-8755-0.94-V1.patch, HBASE-8755-trunk-V0.patch
>
>
> In current write model, each write handler thread (executing put()) will individually
go through a full 'append (hlog local buffer) => HLog writer append (write to hdfs) =>
HLog writer sync (sync hdfs)' cycle for each write, which incurs heavy race condition on updateLock
and flushLock.
> The only optimization where checking if current syncTillHere > txid in expectation
for other thread help write/sync its own txid to hdfs and omitting the write/sync actually
help much less than expectation.
> Three of my colleagues(Ye Hangjun / Wu Zesheng / Zhang Peng) at Xiaomi proposed a new
write thread model for writing hdfs sequence file and the prototype implementation shows a
4X improvement for throughput (from 17000 to 70000+).
> I apply this new write thread model in HLog and the performance test in our test cluster
shows about 3X throughput improvement (from 12150 to 31520 for 1 RS, from 22000 to 70000 for
5 RS), the 1 RS write throughput (1K row-size) even beats the one of BigTable (Precolator
published in 2011 says Bigtable's write throughput then is 31002). I can provide the detailed
performance test results if anyone is interested.
> The change for new write thread model is as below:
> 1> All put handler threads append the edits to HLog's local pending buffer; (it notifies
AsyncWriter thread that there is new edits in local buffer)
> 2> All put handler threads wait in HLog.syncer() function for underlying threads
to finish the sync that contains its txid;
> 3> An single AsyncWriter thread is responsible for retrieve all the buffered edits
in HLog's local pending buffer and write to the hdfs (hlog.writer.append); (it notifies AsyncFlusher
thread that there is new writes to hdfs that needs a sync)
> 4> An single AsyncFlusher thread is responsible for issuing a sync to hdfs to persist
the writes by AsyncWriter; (it notifies the AsyncNotifier thread that sync watermark increases)
> 5> An single AsyncNotifier thread is responsible for notifying all pending put handler
threads which are waiting in the HLog.syncer() function
> 6> No LogSyncer thread any more (since there is always AsyncWriter/AsyncFlusher threads
do the same job it does)
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